The invention relates to a system for copy protection of recorded information, includes an information carrier having a medium mark representing a first bitpattern, a recorder for recording the information on the information carrier and a player for reproducing the recorder information from the information carrier.
The invention further relates to a recorder for recording information on an information carrier with a medium mark representing a bitpattern.
The invention further relates to an information carrier with recorded information and a medium mark representing a bitpattern.
The invention further relates to a player for reproducing information from an information carrier and the system including for detecting a medium mark representing a bitpattern.
Copy protection has a long history in audio publishing. The presently installed base of equipment, including PC's with audio cards, provide little protection against unauthorized copying. In any copy-protection scheme, the most difficult issue is that a pirate can always attempt to playback an original disc, he can treat the content as if it were an analog home recording and record this. Consumer recorders should be able to copy recordings of consumer's own creative productions without any limitation, but prohibit the recording of copy-right material. Thus, the copy protection mechanism must be able to distinguish between consumers' own creations and content that originates from professional music publishers. The equipment must make this distinction based on the content only, as any reference to the physical source of content (e.g. disc or microphone) is unrealiable. For digital storage media such as DCC, “copy bits” have been defined, which bits indicate a copyright status, e.g. “no copy allowed”, “free copy” or “one generation of copy allowed”. Other copy bits may indicate that the medium storing the information must be a “professional” medium manufactured by pressing and not a “recordable” disc.
A system for copy protection of recorded information comprising a recorder, information carrier and player, is known from EP-0545472 corresponding to U.S. Pat. No. 5,724,327 to Timmermans et al. (listed as document D1 below). The copy protection is based on a so-called medium mark, i.e. a physical mark representing a bitpattern indicating the status of the medium, e.g. a code indicating a “professional” disk manufactured by pressing. A medium mark should not be copyable or changeable by standard recording equipment, and therefore it is to be stored on the information carrier in a manner different from the recorded information, such as audio or video. The medium mark is detected by the player and if it is not present or indicates a different status (e.g. “recordable disc” on an illegal copy), reproduction is blocked. The known information carrier has a prearranged guiding track, a so-called pregroove. In the track determined by the pregroove, information can be written in a predefined manner represented by optically readable patterns which are formed by variation of a first physical parameter, such as the height of the scanned surface. The pregroove has variations in a second physical parameter, such as an excursion in a transverse direction, also denoted as wobble. The wobble is FM modulated and this modulation represents a bitpattern which is used for recovering the information, e.g. a descramble code for recovering information stored as scrambled information. The bitpattern constitutes a medium mark, because the track wobble cannot be copied to a recordable disc on standard recording equipment. The known player includes a reader for reading the optical patterns and recovering apparatus for recovering the bitpattern from the medium mark. The player and information carrier form a system for controlled information reproduction. For this purpose, the player has apparatus for controlling the reproducing of the information depending on the medium mark. If the information is copied on a writable information carrier, the information of this copy will not be reproduced by a player, because during the writing process only the optical patterns are written in the predefined manner and the copy itself does not contain any medium mark.
Those skilled in the art are referred to the following documents:                (D1) EP-0545472—corresponding to U.S. Pat. No. 5,724,327 to Timmermans et al. regarding Closed information system with physical copy protection        (D2) WO 97/13248-A1—corresponding to U.S. application Ser. No. 08/723,653 filed Oct. 3,1996 by Linhartz regarding Watermarking encoded signals.        (D3) EP-A 97200197.8 filing date 27 Jan. 1997—corresponding to U.S. application Ser. No. 09/013,540 filed Jan. 26, 1998 regarding Watermarking of Bitstream- or DSD-signals by A. A. M. Bruekers et al.        (D4) U.S. Pat. No. 5,649,054 to Ooman et al. issued Jul. 15, 1997        (D5) WO IB97/01156 corresponding to U.S. application Ser. No. 08/937,435 filed Sep. 25, 1997 regarding Lossless coding for DVD audio A. A. M. Bruekers et al.        (D6) “New Directions in Cryptography” by Diffie and Hellman, IEEE Transactions on information theory, Vol IT-22, No. 6, November 1976, p. 644–654        
The above references are hereby incorporated herein in whole by reference.